A printed circuit board comprises a substrate, typically made of fiberglass or mylar whose surface has metal lines formed thereon which are electrical conductors used to connect various circuit components together and/or to external circuitry. In order to keep pace with the integrated circuit industry, feature sizes, i.e., lines and spaces between the metal lines have shrunk to very small dimensions, e.g., 0.005 inches. While techniques for the fabrication of printed circuit boards have greatly advanced in recent years, a certain percentage of printed circuit boards still come out of production with one or more of a variety of flaws. For example, a printed circuit board may have lines and/or spaces too narrow, shorts, opens, pinholes or the like; any one of which may render the board useless. Due to their extremely small sizes visual detection of such flaws in boards with very fine lines is neither technically effective nor economically practical. Thus, automation of the printed circuit board inspection process is an essential requirement in the printed circuit manufacturing business.
The present invention relates to a system for the automatic inspection of printed circuit boards and the like.